The invention relates to materials useful as thin film protective layers and more particularly to thin film films comprising TiSixNy and even more particularly to such films as used on thin film magnetic media.
A typical prior art head and disk system 10 is illustrated in FIG. 1. In operation the magnetic transducer 20 is supported by the suspension 13 as it flies above the disk 16. The magnetic transducer 20, usually called a xe2x80x9cheadxe2x80x9d, is composed of elements that perform the task of writing magnetic transitions (the write head 23) and reading the magnetic transitions (the read head 12). The electrical signals to and from the read and write heads 12, 23 travel along conductive paths (leads) 14 which are attached to or embedded in the suspension 13. The magnetic transducer 20 is positioned over points at varying radial distances from the center of the disk 16 to read and write circular tracks (not shown). The disk 16 is attached to a spindle 18 that is driven by a spindle motor 24 to rotate the disk 16. The disk 16 comprises a substrate 26 on which a plurality of thin films 21 are deposited. The thin films 21 include ferromagnetic material in which the write head 23 records the magnetic transitions in which information is encoded. The thin film protective layer (not shown in FIG. 1) is typically the last or outermost layer.
The conventional disk 16 typically has a substrate 26 of AlMg/NiP or glass. The thin films 21 on the disk 16 typically include a chromium or chromium alloy underlayer that is deposited on the substrate 26. The magnetic layer in the thin films 21 is based on various alloys of cobalt, nickel and iron. For example, a commonly used alloy is CoPtCr. However, additional elements such as tantalum and boron are often used in the magnetic alloy.
FIG. 2 illustrates one common internal structure of thin films 21 on disk 16. The protective overcoat layer 37 is used to improve wearability and corrosion resistance. The materials and/or compositions which are optimized for one performance characteristic of an overcoat are rarely optimized for others. The most commonly used protective layer materials for commercial thin film disks have been carbon, hydrogenated carbon (CHx), nitrogenated carbon (CNx) and CNxHy. The overcoat on a thin film magnetic disk is subjected to an environment that is quite different from that of a thin film layer in a semiconductor device. The overcoat on a magnetic disk is an integral part of a mechanical system and is thereby subjected to physical impact by the head, contamination by contact with the atmosphere and electrostatic effects caused by intermittant rubbing with the head, i.e., tribocharging. In order to improve the performance of magnetic thin film media the protective overcoat 37 must be made as thin as possible to reduce the separation from the magnetic transducer 20 and the magnetic thin film 33 while maintaining the protective function.
In U.S. Pat. No. 4,761,334 Sagoi, et al., describe the use of SiNx as an overcoat layer for a magnetic thin film disk. Sagoi asserts that silicon oxide, aluminum oxide, titanium nitride make brittle overcoats which are prone to excessive wear from contact with the head. U.S. Pat. No. 6,136,421 to Chen describes the use of silicon nitride oxide as part of a bilayer overcoat which has a layer of amorphous carbonaceous layer over it.
The applicants disclose a overcoat layer of TiSixNy for use on a magnetic thin film disk. The overcoat of the invention has high hardness, provides corrosion protection and has low surface energy which reduces contaminant attraction. The TiSixNy film is conductive and, therefore, reduces the deleterious effects of tribocharging.